Dialysis Access Surveillance Flashcards

Which Doppler parameter is most commonly used to define hemodynamically significant stenosis in a dialysis AVF?

Answer: Peak systolic velocity ratio >2:1 at stenosis

A peak systolic velocity ratio greater than 2:1 across a stenotic segment indicates hemodynamically significant stenosis in AVF surveillance.

A hemodialysis patient's access flow drops from 1,200 mL/min to 550 mL/min over two months. What is the most appropriate next step?

Answer: Refer for fistulogram and intervention

A >25% decrease in access flow below 500 mL/min warrants urgent referral for fistulogram and possible angioplasty to prevent thrombosis.

During duplex surveillance of an AVG, you identify a peak systolic velocity of 450 cm/s within the graft body. The proximal inflow velocity is 120 cm/s. What does this indicate?

Answer: Intragraft stenosis with velocity ratio >3:1

A velocity ratio of 450/120 = 3.75:1 far exceeds the 2:1 threshold, confirming significant intragraft stenosis.

Which finding on duplex ultrasound is most suggestive of venous outflow stenosis in a dialysis AV fistula?

Answer: Pulsatile waveform throughout the fistula

Outflow stenosis causes increased resistance, converting the normally low-resistance venous waveform to a pulsatile pattern throughout the fistula.

What is the recommended minimum access flow threshold below which AVF thrombosis risk is substantially elevated?

Answer: 500 mL/min

Access flow below 500 mL/min in an AVF is associated with significantly increased risk of thrombosis and is an intervention threshold.

A patient presents with arm swelling and collateral veins on the chest wall. Duplex ultrasound of the access shows markedly elevated cephalic vein velocities. What is the likely diagnosis?

Answer: Central venous stenosis

Chest wall collaterals and arm swelling in a dialysis patient indicate central venous stenosis or occlusion, often subclavian or innominate vein.

When performing transonic dilution flow measurement during hemodialysis, what does a decrease in ultrasound signal downstream indicate?

Answer: Indicator dilution as saline passes the sensor

In transonic flow measurement, saline injected upstream causes a transient decrease in ultrasound signal at the downstream sensor used to calculate access blood flow.